Method of making semiconductor device

ABSTRACT

A semiconductor photoelectric conversion device has a conductive substrate or a first conductive layer formed on a suitable substrate, a non-single-crystal semiconductor laminate member formed on the conductive substrate or first conductive layer, including at least one I-type non-single-crystal semiconductor layer and having formed therein at least one PI, NI, PIN, or NIP junction, and a second conductive layer formed on the non-single-crystal semiconductor laminate member. The I-type non-single-crystal semiconductor layer of the non-single-crystal semiconductor laminate member contains oxygen, carbon, or phosphorus only in such a low concentration as 5×10 18  atoms/cm 3  or less, 4×10 18  atoms/cm 3  or less, or 5×10 15  atoms/cm 3  or less, respectively.

This is a divisional application Ser. No. 525,459, filed Aug. 22, 1983,now U.S. Pat. No. 4,591,892.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvement in or relating to asemiconductor photoelectric conversion device which has a conductivesubstrate or a first conductive layer formed on a suitable substrate, anon-single-crystal semiconductor laminate member formed on theconductive substrate or the first conductive layer, including at leastone I-type non-single-crystal semiconductor layer and having formedtherein at least one PI, NI, PIN, or NIP junction, and a secondconductive layer formed on the non-single-crystal semiconductor laminatemember.

2. Description of the Prior Art

Heretofore there have been proposed a variety of semiconductorphotoelectric conversion devices of the type that has a conductivesubstrate or a first conductive layer fomred on a suitable substrate, anon-single-crystal semiconductor laminate member formed on theconductive substrate or the first conductive layer, including at leastone I-type non-single-crystal semiconductor layer and having formedtherein at least one PI, NI, PIN OR NIP junction, and a secondconductive layer formed on the non-single-crystal semiconductor laminatemember.

In the semiconductor photoelectric conversion device of such astructure, the I-type non-single-crystal semiconductor layer has thefunction of generating photo carriers corresponding to the incidencethereon of light. The I-type non-single-crystal semiconductor layercontains hydrogen or a halogen as a recombination center neutralizer, bywhich recombination centers are neutralized which would otherwise existin large quantities since the I-type non-single-crystal semiconductorlayer is formed of a non-single-crystal semiconductor. This preventsphoto carriers created in the I-type non-single-crystal semiconductorlayer from being lost by recombination.

The conventional semiconductor photoelectric conversion devices of thiskind have a low photoelectric conversion efficiency of 8% or less.

As a result of various experiments, the present inventor has found thatone of the reasons for such a low photoelectric conversion efficiency ofthe conventional photoelectric conversion devices is that when theI-type non-single-crystal semiconductor layer of the non-single-crystalsemiconductor laminate member having the function of creating photocarriers is unavoidably formed to contain oxygen as an impurity, theoxygen content is as high as 10²⁰ atoms/cm³ or more.

Further, the present inventor has found that another reason for such alow photoelectric conversion efficiency is that when the I-typenon-single-crystal semiconductor layer is unavoidably formed to containcarbon as an impurity, the carbon content is as high as 10²⁰ atoms/cm³or more.

Besides, the present inventor has found that another reason for such alow photoelectric conversion efficiency is that when the I-typenon-single-crystal semiconductor layer is formed to contain phosphorus,the phosphorus content as an impurity is as high as 5×10¹⁶ atoms/cm³ ormore.

Moreover, the present inventor has found that when the oxygen content inthe I-type non-single-crystal semiconductor layer is as high as 10²⁰atoms/cm³ or more, the semiconductor photoelectric conversion deviceprovides a low photoelectric conversion efficiency of 8% or less for thefollowing reason:

In the case where the I-type non-single-crystal semiconductor layercontains oxygen in as high a concentration as 10²⁰ atoms/cm³ or more, alarge number of clusters of oxygen are formed in the I-typenon-single-crystal semiconductor layer and these clusters of oxygenserve as recombination centers of photo carriers.

Accordingly, when the oxygen content is as high as mentioned above, theI-type non-single-crystal semiconductor layer contains a number ofrecombination centers of photo carriers which are not neutralized by arecombination center neutralizer. Consequently, photo carriers which aregenerated by the incidence of light in the I-type non-single-crystalsemiconductor layer are recombined at the recombination centers,resulting in a great loss of the photo carriers.

Further, the I-type non-single-crystal semiconductor layer, whencontaining oxygen, generates dangling bonds of oxygen, which serve asdonor centers. In the case where the I-type non-single-crystalsemiconductor layer contains oxygen in such a high concentration as 10²⁰atoms/cm³ or more, it contains many dangling bonds of oxygen acting asdonor centers. In this case, the midpoint level of the energy band inthe I-type non-single-crystal semiconductor layer relatively shifts moretowards the valence band than does the Fermi level. Accordingly, theefficiency of photo carriers generation based on the amount of lightincident the I-type non-single-crystal semiconductor layer is very low.Further, the diffusion length of holes of the photo carriers in theI-type non-single-crystal semiconductor layer is short. This leads tolow photoconductivity and very high dark conductivity of the I-typenon-single-crystal semiconductor layer.

Moreover, when the I-type non-single-crystal semiconductor layercontains oxygen, the oxygen is combined with the material forming thelayer. For instance, when the layer is formed of silicon, it has acombination with oxygen expressed as Si-O-Si. Accordingly, when theoxygen content is as high as 10²⁰ atoms/cm³ or more, the layer containsa large amount the combination of the material forming the layer andoxygen.

On the other hand, the combination of the material forming the I-typenon-single-crystal semiconductor layer and the oxygen contained thereinis decomposed by the irradiation of light to create in the layerdangling bonds of the material forming it and dangling bonds of theoxygen.

Accordingly, in the case where the I-type non-single-crystalsemiconductor layer contains oxygen in such a high concentration as 10²⁰atoms/cm³ or more, the dangling bonds of the material forming the layerand the dangling bonds of oxygen, which are generated in the layer,greatly increase by the irradiation of light. In such as case, thedangling bonds of the material forming the layer act as recombinationcenters of the photo carriers, and the loss of photo carriers generatedin the layer increases. When the number of dangling bonds of oxygenincreases, the midpoint level of the energy band, which has shifted muchfurther towards the valence band than the Fermi level, shifts furthertowards the valence band correspondingly, resulting in marked reductionof the photo carrier generating efficiency of the I-typenon-single-crystal semiconductor layer. Also the diffusion length ofholes in the I-type non-single-crystal semiconductor layer is furtherreduced, markedly lowering the photoconductivity and raising the darkconductivity of the layer.

When the photocarrier generating efficiency and the photoconductivity ofthe I-type non-single-crystal semiconductor layer have thus been loweredand the loss of the photo carriers in the layer and the darkconductivity of the layer have thus been increased, if the layer isheated, the dangling bonds of the material forming the layer and thedangling bonds of oxygen, generated in large quantities in the layer,are partly recombined with each other to re-form the combination of thematerial forming the layer and oxygen. As a result, the number ofdangling bonds of the material forming the layer and the amount ofoxygen decreases. In the I-type non-single-crystal semiconductor layer,however, the dangling bonds of the material forming the layer and thedangling bonds of oxygen still remain in large quantities. Consequently,the photo carrier generating efficiency and the photoconductivity of theI-type non-single-crystal semiconductor layer are very low and result aloss of photo carriers in the layer, and the dark conductivity of thelayer is extremely high. In addition, the values of the photo carriergenerating efficiency, the photoconductivity, the loss of photo carriersand the dark conductivity of the I-type non-single-crystal semiconductorlayer differ significantly before and after irradiation by light andafter heating.

The above is the reason found by the present inventor why thephotoelectric conversion efficiency of the conventional semiconductorphotoelectric conversion device is as low as 8% or less when the I-typenon-single-crystal semiconductor layer contains oxygen in such a highconcentration as 10²⁰ atoms/cm³ or more.

Further, the present inventor has found that when the I-typenon-single-crystal semiconductor layer contains carbon in such a highconcentration as 10²⁰ atoms/cm³ or more, the photoelectric conversionefficiency of the conventional semiconductor photoelectric conversiondevice is as low as 8% or less for the following reason:

When the I-type non-single-crystal semiconductor layer contains carbonin such a high concentration as 10²⁰ atoms/cm³ as referred topreviously, the layer forms therein a number of clusters of carbon. Theclusters of carbon act as combination centers of photo carriers as isthe case with the clusters of oxygen. Accordingly, when the I-typenon-single-crystal semiconductor layer contains carbon in such a highconcentration as 10²⁰ atoms/cm³ or more, a great loss of the carriersthat are created in the layer due to incidence thereon of light results.

The above is the reason found by the present inventor why thephotoelectric conversion efficiency of the conventional semiconductorphotoelectric conversion device is 8% or less when the I-typenon-single-crystal semiconductor layer contains carbon in such a highconcentration as 10²⁰ atoms/cm³ or more.

Moreover, the present invention has found that when the I-typenon-single-crystal semiconductor layer contains phosphorus in such ahigh concentration as 5×10¹⁶ atoms/cm³ or more, the photoelectricconversion efficiency of the conventional semiconductor photoelectricconversion device is as low as 8% or less for the following reason:

In the case where the phosphorus content in the I-typenon-single-crystal semiconductor layer is as high as 5×10¹⁶ atoms/cm³ ormore, the midpoint level of the energy band in the I-type layer shiftsmore towards the valence band than the Fermi level does, as in the caseof the layer containing oxygen in such a high concentration as 10²⁰atoms/cm³ or more. Accordingly, the photocarrier generating efficiencyof the I-type non-single-crystal semiconductor layer is very low.Further, the diffusion length of holes of the photo carriers generatedin the layer is short, and hence the photoconductivity of the layer islow and its dark conductivity is very high.

The above is the reason found by the present inventor why thephotoelectric conversion efficiency of the conventional semiconductorphotoelectric conversion device is as low as 8% or less when thephosphorus content is higher than 5×10¹⁶ atoms/cm³.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a novelsemiconductor photoelectric conversion device which is provided with aconductive substrate or a first conductive layer formed on a suitablesubstrate, a non-single-crystal semiconductor laminate member formed onthe conductive substrate or the first conductive layer, including atleast one I-type non-single-crystal semiconductor layer and havingformed therein at least one PI, NI, PIN, or NIP junction, and a secondconductive layer formed on the non-single-crystal semiconductor laminatemember and which is much higher in photoelectric conversion efficiencythan conventional semiconductor photoelectric conversion devices of theabovesaid construction.

In accordance with an aspect of the present invention, even if theI-type non-single-crystal semiconductor layer of the non-single-crystalsemiconductor laminate member which has the function of generating photocarriers is unavoidably formed to contain oxygen as an impurity, theoxygen content is low, 5×10¹⁸ atoms/cm³ or less.

In accordance with another aspect of the present invention, even if theI-type non-single-crystal semiconductor layer of the non-single-crystalsemiconductor laminate member is unavoidably formed to contain carbon asan impurity, the carbon content is low, 4×10¹⁸ atoms/cm³ or less.

In accordance with another aspect of the present invention, even if theI-type non-single-crystal semiconductor layer of the non-single-crystalsemiconductor laminate member is unavoidably formed to containphorphorus as an impurity, the phosphorus content is low, 5×10¹⁵atoms/cm³ or less.

Therefore, the semiconductor photoelectric conversion device of thepresent invention has a far higher photoelectric conversion efficiencythan the conventional semiconductor photoelectric conversion devices ofthis kind.

The reason why the photoelectric conversion efficiency when the oxygencontent is 5×10¹⁸ atoms/cm³ or less is much higher than thephotoelectric conversion efficiency than when the oxygen content is 10²⁰atoms/cm³ or more as described previously in connection with the priorart, is the following:

When the oxygen content of the I-type non-single-crystal semiconductorlayer is 5×10¹⁸ atoms/cm³ or less, there is formed in the layer few ifany clusters of oxygen which act as recombination centers of photocarriers. Accordingly, the I-type non-single-crystal semiconductor layerhas few if any recombination centers of photo carriers based on oxygen.Consequently, little if any loss of photo carriers that are created inthe I-type non-single-crystal semiconductor layer occurs.

When the oxygen content of the I-type non-single-crystal semiconductorlayer is 5×10¹⁸ atoms/cm³ or less, the number of dangling bonds ofoxygen contained in the layer is very small. Accordingly, the midpointlevel of the energy band of the I-type non-single-crystal semiconductorlayer hardly shifts from the Fermi level and even if it does shift, theamount of deviation is very small. Consequently, the photo carriergenerating efficiency and the photoconductivity of the layer are muchhigher than those obtainable with the conventional semiconductorphotoelectric conversion device in which the oxygen content of theI-type non-single-crystal semiconductor layer is 10²⁰ atoms/cm³ or more,and the dark conductivity of the layer is much lower than in the case ofthe prior art device.

Further, when the oxygen content of the I-type non-single-crystalsemiconductor layer is 5×10¹⁸ atoms/cm³ or less, even if the layercontains combinations of the material forming the layer and the oxygen,the number of such combinations is very small. Accordingly, danglingbonds of the material forming the layer and oxygen are not substantiallyformed by irradiation or the semiconductor photoelectric conversiondevice by light and, even if they are formed, their number is verysmall. Further, even if the device is heated, the dangling bonds of thematerial forming the layer and the dangling bonds of oxygen do notincrease. The photo carrier generating efficiency, the photoconductivity and the dark conductivity of the layer do not substantiallydiffer before and after irradiation by light and after heating.

The above is the reason why when the oxygen content of the I-typenon-single-crystal semiconductor layer is 5×10¹⁸ atoms/cm³ or less, thesemiconductor photoelectric conversion device of the present inventionexhibits a much higher photoelectric conversion efficiency than theconventional semiconductor photoelectric conversion device in which theoxygen content of the I-type non-single-crystal semiconductor layer is10²⁰ atoms/cm³ or more.

The reason why the photoelectric conversion efficiency when the carboncontent is 4×10¹⁸ atoms/cm³ or less is much higher than thephotoelectric conversion efficiency when the carbon content is 10²⁰atoms/cm³ or more as described previously with respect to the prior art,is the following:

When the carbon content of the I-type non-single-crystal semiconductorlayer is 4×10¹⁸ atoms/cm³ or less, there is formed in the layer few, ifany clusters of carbon which act as recombination centers of photocarriers. Accordingly, the I-type non-single-crystal semiconductor layerhas few, if any combination centers of photo carriers based on cabon.Consequently, little, if any loss of the photo carriers that are createdin the I-type non-single-crystal semiconductor layer occurs.

The above is the reason why when the carbon content of the I-typenon-single-crystal semiconductor layer is 4×10¹⁸ or less, thesemiconductor photoelectric conversion device of the present inventionexhibits a much higher photoelectric conversion efficiency than does theconventional semiconductor photoelectric conversion device in which thecarbon content of the I-type non-single-crystal semiconductor layer is10²⁰ atoms/cm³ or more.

The reason why the photoelectric conversion efficiency when thephosphorous content is 5×10¹⁵ atoms/cm³ or less is much higher than thephotoelectric conversion efficiency when the phosphorus content is5×10¹⁶ atoms/cm³ or more as referred to previously with respect to theprior art, is the following:

When the phosphorus content of the I-type non-single-crystalsemiconductor layer is 5×10¹⁵ atoms/cm³ or less, even if the layercontains dangling bonds of phosphorus, their number is very small.Accordingly, the midpoint level of the energy band of the I-typenon-single-crystal semiconductor layer scarcely shifts from the Fermilevel and even if it does shift, the amount of deviation is very small.Consequently, the photo carrier generating efficiency and thephotoconductivity of the layer are much higher than those obtainablewith the conventional semiconductor photoelectric conversion device inwhich the phosphorus content of the I-type non-single-crystalsemiconductor layer is 5×10¹⁶ atoms/cm³ or more, and the darkconductivity of the layer is much lower than in the case of the priorart device.

The above is the reason why when the phosphorus content of the I-typenon-single-crystal semiconductor layer is 5×10¹⁵ atoms/cm³ or less, thesemiconductor photoelectric conversion device of the present inventionexhibits a much higher photoelectric conversion efficiency than does theconventional semiconductor photoelectric conversion device in which thephosphorus content of the I-type non-single-crystal semiconductor layeris 5×10¹⁶ atoms/cm³ or more.

Other objects, features and advantages of the present invention willbecome more fully apparent from the following detailed description takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic cross-sectional views respectivelyillustrating first and second embodiments of a semiconductorphotoelectric conversion device to which the present invention isapplicable.

FIG. 3 is a graph showing the relationships of the photoconductivity anddark conductivity of an I-type non-single-crystal semiconductor layer ofa non-single-crystal semiconductor laminate member and the oxygencontent of the layer in the semiconductor photoelectric conversiondevices of FIGS. 1 and 2;

FIG. 4 is a graph showing the relationships of the photoconductivity anddark conductivity of the I-type non-single-crystal semiconductor layerof the non-single-crystal semiconductor laminate member and the carboncontent of the layer in the semiconductor photoelectric conversiondevices of FIGS. 1 and 2;

FIG. 5 is a graph showing the relationships of the photoconductivity anddark conductivity of the I-type non-single-crystal semiconductor layerof the non-single-crystal semiconductor laminate and the phosphoruscontent of the layer in the semiconductor photoelectric conversiondevices of FIGS. 1 and 2;

FIG. 6 is a graph showing the relationships of the photoelectricconversion efficiency, short-circuit current, and fill factor of thesemiconductor photoelectric conversion devices of FIGS. 1 and 2 to theoxygen content of the I-type non-single-crystal semiconductor layer;

FIG. 7 is a graph showing the relationships of the photoelectricconversion efficiency, short-circuit current, and fill factor of thesemiconductor photoelectric conversion devices of FIGS. 1 and 2 to thecarbon content of the I-type non-single-crystal semiconductor layer;

FIG. 8 is a graph showing the relationships of the photoelectricconversion efficiency, short-circuit current, and fill factor of thesemiconductor photoelectric conversion devices of FIGS. 1 and 2 to thephosphorus content of the I-type non-single-crystal semiconductor layer;and

FIGS. 9 and 10 are graphs showing the relationships of the normalizedphotoelectric conversion efficiency of the semiconductor photoelectricconversion devices of FIGS. 1 and 2 to the wavelengths of light beforeand after irradiation of the devices by light and after heating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate first and second embodiments of thesemiconductor photoelectric conversion device to which the presentinvention is applicable.

The embodiment of the semiconductor photoelectric conversion device ofFIG. 1 to which the present invention is applicable has the followingconstruction:

A light transparent conductive layer 2 such as tin oxide is formed, forexample, by vacuum deposition on an insulating and light transparentsubstrate 1 such as glass.

On the light transparent conductive layer 2 is formed anon-single-crystal semiconductor laminate member 3. Thenon-single-crystal semiconductor laminate member 3 is formed by asequential lamination of, for instance, a P-type non-single-crystalsemiconductor layer 4, an I-type non-single-crystal semiconductor layer5 containing hydrogen or a halogen as a recombination centerneutralizer, and an N-type non-single-crystal semiconductor layer 6.Accordingly, the non-single-crystal semiconductor laminate member 3 hasone I-type non-single-crystal semiconductor layer 5 and has formedtherein one PIN junction. In this case, the P-type non-single-crystalsemiconductor layer 4 is formed of silicon (Si), Si_(x) C_(1-x) (0<x<1,where x=0.8, for instance), germanium (Ge) or the like, and the layer 4is, for instance, 100 Å thick. When the P-type non-single-crystalsemiconductor layer 4 is formed of silicon or Si_(x) C_(1-x), the I-typenon-single-crystal semiconductor layer 5 is formed of silicon or Si_(x)Ge_(1-x), and when the layer 4 is formed of Ge, the layer 5 is formed ofGe. The layer 5 has a thickness of, for example, 0.5 μm. Further, whenthe I-type non-single-crystal semiconductor layer 5 is formed of siliconor Si_(x) Ge_(1-x), the N-type non-single-crystal semiconductor layer 6is formed of silicon or Si_(x) C_(1-x) (x=0.9, for example), and whenthe layer 5 is formed of germanium or Si_(x) Ge_(1-x), the layer 6 isformed of germanium or Si_(x) Ge_(1-x). The N-type non-single crystalsemiconductor layer 6 is, for example, 200 Å in thickness.

The non-single-crystal semiconductor layers 4, 5, and 6 making up thenon-single-crystal semiconductor laminate member 3 are successivelyformed by a CVD method which does not employ a glow discharge, or aplasma CVD method which employs a glow discharge.

On the non-single-crystal semiconductor laminate member 3 is formed, forexample, by vacuum deposition a reflective conductive layer 7 such as ofaluminum.

The above is a description of the structure of the first embodiment ofthe semiconductor photoelectric conversion device to which the presentinvention is applicable.

The second embodiment of the semiconductor photoelectric conversiondevice of FIG. 2 to which the present invention is applicable has thefollowing construction:

On a reflective conductive substrate 11 such as stainless steel isformed the non-single-crystal semiconductor laminate member 3 as is thecase with the semiconductor photoelectric conversion device shown inFIG. 1.

The non-single-crystal semiconductor laminate member 3 is formed by asequential lamination of the P-type non-single-crystal semiconductorlayer 4, the I-type non-single-crystal semiconductor layer 5 containinghydrogen or a halogen as a recombination center neutralizer, and theP-type non-single-crystal semiconductor layer 6, as is the case with thenon-single-crystal semiconductor laminate member 3 in FIG. 1.Accordingly, the non-single-crystal semiconductor laminate member 3 hasone I-type non-single-crystal semiconductor layer 5 and has formedtherein one PIN junction, as is the case with the non-single-crystalsemiconductor laminate member 3 in FIG. 1. The non-single-crystalsemiconductor layers 4, 5, and 6 are also formed by a CVD method such asmentioned above.

On the non-single-crystal semiconductor laminate member 3 is formed, forinstance, by vacuum deposition a light transparent conductive layer 12such as indium oxide containing tin oxide, which corresponds to theconductive layer 2 in FIG. 1.

Further, a conductive layer 13 for external connection use is formed onthe conductive layer 12.

The above is a description of the structure of the second embodiment ofthe semiconductor photoelectric conversion device to which the presentinvention is applicable.

The first and second embodiments of FIGS. 1 and 2 are essentiallyidentical in construction with known semiconductor photoelectricconversion devices.

With the structure of the semiconductor photoelectric conversion deviceshown in FIG. 1, when light 8 impinges on the device from outside thesubstrate 1, it reaches the I-type non-single-crystal semiconductorlayer 5 of the non-single-crystal semiconductor laminate member 3 tocreate therein photo carriers. Accordingly, if a load is connectedacross the light transparent conductive layer 2 and the reflectiveconductive layer 7, power is supplied to the load. With the structure ofthe semiconductor photoelectric conversion device of FIG. 2, the light 8incident on the light transparent conductive layer 12 reaches the I-typenon-single-crystal semiconductor layers 5 of the non-single-crystalsemiconductor laminate member 3 to generate therein photocarriers, as isthe case of the device shown in FIG. 1. Accordingly, if a load isconnected across the reflective conductive substrate 11 and the lighttransparent conductive layer 12, power is supplied to the load.

When the I-type non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor laminate member 3 is formed of siliconby the CVD method using, for example, silane (SiH₄) gas as asemiconductor raw material gas, it inevitably contains oxygen, carbon,and phosphorus.

The reason for this is that it is extremely difficult to remove oxygen,carbon and phosphorus from the silane gas when it is prepared.

Incidentally, commercially available silane gas of 99.99% purity usuallycontains oxygen at about 0.1 ppm in the form of a molecular oxygen (O₂)and about 3 ppm in the form of water (H₂ O); carbon at about 5 ppm inthe form of methane (CH₄) and about 0.1 ppm in the form of ethane (C₂H₆), ethylene (C₂ H₄), propane (C₃ H₈), and propylene (C₃ H₆); andphosphorus at about 0.1 ppm in the form of phosphine (PH₃).

Further, when the I-type non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor laminate member 3 is formed ofgermanium by the CVD method using, for example, germane (GeH₄) gas asthe semiconductor material gas, the layer 5 inevitably contains oxygen,carbon, and phosphorus because it is extremely difficult in practice toremove them from the germane gas when it is prepared.

Moreover, when the I-type non-single-crystal semiconductor layer 5 ofthe non-single-crystal semiconductor laminate member 3 is formed ofSi_(x) Ge_(1-x) by the CVD method using, as the semiconductor materialgas, a mixture of silane and germane gases, the layer 5 inevitablycontains oxygen, carbon, and phosphorus because it is extremelydifficult, in practice, to prepare the silane and germane gases withsubstantially no oxygen, carbon, and phosphorus contents.

In the conventional photoelectric device similar to those of FIGS. 1 and2, the I-type non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor laminate member 3 contains oxygen in ahigh concentration exceeding 10²⁰ atoms/cm³, carbon in a highconcentration exceeding 10²⁰ atoms/cm³, or and/or phosphorus in a highconcentration exceeding 5×10¹⁶ atoms/cm³.

In contrast thereto, according to the present invention, even if theI-type non-single-crystal semiconductor layer 5 of thenon-single-crystal semiconductor laminate members 3 unavoidably containsoxygen, the oxygen content is only 5×10¹⁸ atoms/cm³ or less.

The I-type non-single-crystal semiconductor layer 5 with such a smalloxygen content can be formed by using, as the semiconductor raw materialgas in the case of forming the layer of silicon through the CVD methodas mentioned above, a silane gas which is obtained by passing a rawsilane gas of high purity through a molecular sieve having a meshdiameter of 2.7 to 4.65 Å or a zeolite having a pore diameter of thesame size so that the oxygen content of the silane gas may be reduced tosubstantially zero or a negligibly small amount.

The reason why such a silane gas with essentially no oxygen can beobtained from the raw silane gas by using a molecular sieve or zeolite,is as follows: The effective molecular diameter of the silane is largerthan 4.65 Å and when oxygen is contained in the form of O₂ and H₂ O inthe raw silane gas as referred to previously, their molecular diametersare within 2.7 to 4.65 Å, so that the silane cannot pass through themeshes of the molecular sieve or the pores of the zeolite and hence isnot adsorbed on the moelcular sieve or zeolite, whereas the oxygen andwater contained in the raw silane gas pass through the meshes of themolecular sieve or the pores of the zeolite and are effectively adsorbedthereon.

The oxygen content of such a silane gas can be further reduced bypassing it through a deoxidizing agent. By using thus obtained silanegas, the oxygen content of the I-type non-single-crystal semiconductorlayer 5 can be further reduced.

Further, according to the present invention, even if the I-typenon-single-crystal semiconductor layer 5 of the non-single-crystalsemiconductor laminate member 3 unavoidably contains carbon, the carboncontent is only 4×10¹⁸ atoms/cm³ or less.

The I-type non-single-crystal semiconductor layer 5 with such a smallcarbon content can be formed by using, as the semiconductor material gasin the case of forming the layer of silicon through the CVD method asmentioned above, a silane gas which is obtained by passing a raw silanegas of high purity through a molecular sieve having a mesh diameter of2.7 to 4.65 Å or a zeolite having a pore diameter of the same size sothat the carbon content of the silane gas may be reduced tosubstantially zero or a negligibly small amount.

The reason why such a silane gas with essentially no carbon can beobtained from the raw silane gas through using the molecular sieve orzeolite, is as follows: The effective molecular diameter of the silaneis larger than 4.65 Å and when carbon is contained in the form ofethane, ethylene, propane, and propylene in the raw silane gas asreferred to previously, their molecular diameters are within 2.7 to 4.65Å, so that the ethane, ethylene, propane, and propylene contained in theraw silane gas pass through the meshes of the molecular sieve or thepores of the zeolite and are effectively adsorbed thereon.

Further, according to the present invention, even if the I-typenon-single-crystal semiconductor layer 5 of the non-single-crystalsemiconductor laminate member 3 unavoidably contains phosphorus, thephosphorus content is only 5×10¹⁵ atoms/cm³ or less.

The I-type non-single-crystal semiconductor layer 5 with such a smallphosphorus content can be formed by using, as the semiconductor materialgas in the case of forming the layer of silicon through the CVD methodas mentioned above, a silane gas which is obtained by passing a rawsilane gas of high purity through a molecular sieve having a meshdiameter of 4.5 Å or a zeolite having a pore diameter of the same sizeso that the phosphorus content of the silane gas may be reduced tosubstantially zero or a negligibly small amount.

The reason why such a silane gas with essentially no phosphorus can beobtained from the raw silane gas through using the molecular sieve orzeolite, is as follows: the effective molecular diameter of the silaneis larger than 4.8 Å. and when phosphorus is contained in the form ofphosphine in the raw silane gas as referred to previously, its moleculardiameter is 4.5 Å, so that the phosphine contained in the raw silane gaspasses through the meshes of the molecular sieve or the pores of thezeolite and is effectively adsorbed thereon.

Thus, according to the present invention, the I-type non-single-crystalsemiconductor layer 5 contains oxygen in a low concentration such as5×10¹⁸ atoms/cm³ or less, carbon in a low concentration such as 4×10¹⁸atoms/cm³ or less and phosphorus in a low concentration such as 5×10¹⁵atoms/cm³ or less.

Therefore, according to the embodiments of the present invention shownin FIGS. 1 and 2, the photoconductivity of the I-type non-single-crystalsemiconductor layer 5 is higher than that of the I-typenon-single-crystal semiconductor layer of the conventional photoelectricconversion device which contains oxygen in a high concentration such as10²⁰ atoms/cm³ or more, carbon in a high concentration such as 10²⁰atoms/cm³ or more and phosphorus in a high concentration such as 5×10¹⁶atoms/cm³ or more.

FIGS. 3 to 5 show this.

That is, in the case where the carbon content and the phosphorus contentof the I-type non-single-crystal semiconductor layer 5 are 3×10²⁰ and5×10¹⁶ atoms/cm³, respectively, the photoconductivity (Ωcm)⁻¹ of thelayer 5 as a function of the oxygen content (atom/cm³) thereof is asindicated by curve C-1A in FIG. 3. In the case where the carbon contentand the phosphorus content of the layer 5 are 4×10¹⁸ and 5×10¹⁵atoms/cm³, respectively, the photoconductivity of the layer 5 as afunction of the oxygen content thereof is as indicated by a curve C-1Bin FIG. 3.

In the case where the photoconductivity of the layer 5 is as indicatedby point C-1A' on the curve C-1A in FIG. 3, when the layer 5 containsoxygen in the concentration at the point C-1A', the dark conductivity(Ωcm)⁻¹ of the layer 5 is as indicated by a point D-1A' in FIG. 3. Inthe case where the photoconductivity of the layer 5 is as indicated by apoint C-1B' on the curve C-1B in FIG. 3, when the layer 5 containsoxygen in the concentration at the point C-1B', the dark conductivity ofthe layer 5 is as indicated by point D-1B' in FIG. 3.

Further, in the case where the oxygen content and the phosphorus contentof the I-type non-single-crystal semiconductor layer 5 are 1×10²⁰ and5×10¹⁶ atoms/cm³, respectively, the photoconductivity of the layer 5 asa function of the carbon content thereof is as indicated by curve C-2Ain FIG. 4. In the case where the oxygen content and the phosphoruscontent of the layer 5 are 3×10¹⁷ and 5×10¹⁵ atoms/cm³, respectively,the photoconductivity of the layer 5 as a function of the carbon contentthereof is as indicated by curve C-2B in FIG. 4.

In the case where the photoconductivity of the layer 5 is as indicatedby point C-2A' on the curve C-2A in FIG. 4, when the layer 5 containscarbon in the concentration at the point C-2A', the dark conductivity ofthe layer 5 is as indicated by point D-2A' in FIG. 4. In the case wherethe photoconductivity of the layer 5 is as indicated by a point C-2B' onthe curve C-2B in FIG. 4, when the layer 5 contains carbon in theconcentration at the point C-2B', the dark conductivity of the layer 5is as indicated by point D-2B'in FIG. 4.

Moreover, in the case where the oxygen and carbon contents of the I-typenon-single-crystal semiconductor layer 5 are both 2×10²⁰ atoms/cm³, thephotoconductivity and the dark conductivity of the layer 5 in the casewhen its phosphorus content is 5×10¹⁶ atoms/cm³ is as indicated bypoints C-3A' and D-3A' in FIG. 5, respectively. In the case where theoxygen content and the carbon content of the layer 5 are 5×10¹⁸ and 4×10¹⁸ atoms/cm³, respectively, the photoconductivity and the darkconductivity of the layer 5 as a function of the phosphorus contentthereof are as indicated by curves C-3B and D-3B in FIG. 5,respectively.

As will be appreciated from the above, according to to the presentinvention, the I-type non-single-crystal semiconductor layer 5 has amuch higher photoconductivity than does the I-type non-single-crystalsemiconductor layer of the conventional semiconductor photoelectricconversion device.

Further, according to the present invention, one of the reasons for thehigh photoconductivity of the I-type non-single-crystal semiconductorlayer is that the photoelectric conversion efficiency, the short-circuitcurrent, and the fill factor ((short-circuit current x openvoltage)/maximum power) of the semiconductor photoelectric conversiondevice of the present invention are much higher than those of theconventional semiconductor photoelectric conversion device.

FIGS. 6 to 8 show this.

That is, when the photoconductivity of the I-type non-single-crystalsemiconductor layer 5 is as indicated by the curve C-1B in FIG. 3, thephotoelectric conversion efficiency (%), the short-circuit current(mA/cm²), and the fill factor of the semiconductor photoelectricconversion device as a function of the oxygen content (atom/cm³) of thelayer 5 are such as indicated by curves E-1B, S-1B, and F-2B,respectively, in FIG. 6.

When the photoconductivity of the I-type non-single-crystalsemiconductor layer 5 is as indicated by the curve C-2B in FIG. 4, thephotoelectric conversion efficiency, the short-circuit current, and thefill factor relative to the carbon content of the layer 5 are asindicated by curves E-2B, S-2B, and F-2B, respectively, in FIG. 7.

Further, when the photoconductivity of the I-type non-single-crystalsemiconductor layer 5 is as indicated by the curve C-3B in FIG. 5, thephotoelectric conversion efficiency, the short-circuit current, and thefactor of the semiconductor photoelectric conversion device relative tothe phosphorus content of the layer 5 are as indicated by E-3B, S-3B andF-3B, respectively, in FIG. 8. In this case, the oxygen and carboncontents of the layer 5 are 10³ times the phosphorus content thereof.

Thus, according to the present invention, the photoelectric conversionefficiency, the short-circuit current, and the fill factor of thesemiconductor photoelectric conversion device can be made much higherthan those obtainable with the prior art semiconductor photoelectricconversion device.

Moreover, according to the semiconductor photoelectric conversion deviceof the present invention, its photoelectric conversion efficiency ishardly affected by irradiation by light and, even by heating after thelight irradiation, the photoelectric conversion efficiency undergoes noappreciable changes.

FIGS. 9 and 10 show this.

That is, when the photoconductivity of the I-type non-single-crystalsemiconductor layer 5 is obtained as indicated by the point C-1A' inFIG. 3, the photoelectric conversion efficiency (normalized with respectto a maximum photoelectric conversion efficiency of 1) as a function ofthe wavelength (mm) of incident light is as indicated by curve E-4A inFIG. 9 before irradiation by light and, after the irradiation by light,it becomes as indicated by curve E-5A in FIG. 9 and, by heating at 150°C. for two hours after the irradiation by light, the photoconductivityis as indicated by curve E-6A in FIG. 9.

When the photoconductivity of the I-type non-single-crystalsemiconductor layer 5 is as indicated by the point C-1B' in FIG. 3, thephotoelectric conversion efficiency (normalized as mentioned above) as afunction of the wavelength of incident light is as indicated by curveE-4B in FIG. 10. After irradiation light under the same conditions as inthe case of curve E-5A in FIG. 9, the photoelectric conversionefficiency is as indicated by curve E-5B in FIG. 10 and, by heatingunder the same conditions as mentioned above after the irradiation bylight, the photoelectric conversion efficiency becomes as indicated bycurve E-6B in FIG. 10.

As will be appreciated from the above, according to the presentinvention, the photoelectric conversion efficiency hardly changes and itremains substantially unchanged even if heating is carried out afterirradiation by light.

While the present invention has been described as being applied to asemiconductor photoelectric conversion device in which thenon-single-crystal semiconductor laminate member has a PIN or NIP typestructure and, accordingly, it has formed therein one PIN or NIPjunction, the present invention is also applicable to semiconductorphotoelectric conversion devices in which the non-single-crystalsemiconductor laminate member has an NI, PI, NIN, or PIP type structureand, accordingly, it has formed therein at least one NI, PI, NIN, or PIPjunction.

Also the present invention is applicable to semiconductor photoelectricconversion devices of the type in which the non-single-crystalsemiconductor laminate member has, for example, an NIPIN or PINIP typestructure and, accordingly, has formed therein at least one PIN and NIPjunction.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent invention.

What is claimed is:
 1. A method of making a semiconductor device, saidmethod comprising:forming a non-single-crystal semiconductor laminatemember on a substrate or a conductive layer, said laminate memberincluding at least one I-type non-single-crystal semiconductor layer andhaving formed therein at least one PI, NI, PIN, or NIP junction, saidI-type layer being formed using a silane gas obtained by passing a rawsilane gas of high purity through a passage containing a molecular sievehaving a mesh diameter of 2.7 to 4.65 A or zeolite having a porediameter of the same size; wherein the I-type non-single-crystalsemiconductor layer of the non-single-crystal semiconductor laminatemember contains oxygen only in such a low concentration as 5×10¹⁸atoms/cm³ or less.
 2. A method for making a semiconductor device, saidmethod comprising:forming a non-single-crystal semiconductor laminatemember on a substrate or a conductive layer, said laminate memberincluding at least one I-type non-single-crystal semiconductor layer andhaving formed therein at least one PI, NI, PIN, or NIP junction, saidI-type layer being formed using a silane gas obtained by passing a rawsilane gas of high purity through a passage containing a molecular sievehaving a mesh diameter of 2.7 to 4.65 A or zeolite having a porediameter of the same size; wherein the I-type non-single-crystalsemiconductor layer of the non-single-crystal semiconductor laminatemember contains carbon only in such low concentration as 4×10¹⁸atoms/cm³ or less.
 3. A method of making a semiconductor device, saidmethod comprising:forming a non-single-crystal semiconductor laminatemember on a substrate or a conductive layer, said laminate memberincluding at least one I-type non-single-crystal semiconductor layer andhaving formed therein at least one PI, NI, PIN, or NIP junction, saidI-type layer being formed using a silane gas obtained by passing a rawsilane gas of high purity through a passage containing a molecular sievehaving a mesh diameter of about 4.5 A or zeolite having a pore diameterof the same size; wherein the I-type non-single-crystal semiconductorlayer of the non-single-crystal semiconductor laminate member containsphosphorus only in such low cencentration as 5×10¹⁵ atoms/cm³ or less.4. A method according to claim 1, 2 or 3, wherein the I-typenon-single-crystal semiconductor layer of the non-single-crystalsemiconductor laminate member is formed of silicon, germanium or Si_(x)Ge_(1-x) (0<x<1).
 5. A method according to claim 4, wherein the I-typenon-single-crystal semiconductor layer of the non-single-crystalsemiconductor laminate member contains hydrogen or a halogen as arecombination center neutralizer.
 6. A method according to claims 1, 2,or 3, wherein the silane gas is monosilane expressed by SiH₄.